License Number P.1372
UKCS Block 22/8c
Carrizo Oil & Gas, Inc. (100%)
I. Synopsis
License P.1372 was licensed by Carrizo in December 2005 in the 23rd round as a fouryear promote license, with a two-year drill/drop provision. The block was relinquished
effective December 22, 2007. All work commitments were fulfilled on the block and
there are no suspended wells.
The 27.8 sq km block (6,867 net acres) is located ~150 km (94 miles) offshore in 91
meters of water (300 ft) and contains the Santa Cruz North prospect and a lesser portion
(30%) of the Santa Cruz prospect which overlaps into the adjoining block to the south
(22/13b) which is presently licensed to Oilexco (72.7%) and Carrizo (27.3%). Neither
feature was considered by the Licensee to be large enough to justify a firm well
commitment.
II. Exploration Activities
Carrizo licensed and reprocessed 100 km2 of 3-D (Pre-STM) seismic data across the
block in fulfillment of the license obligations. The data was first acquired by BP, PGS
and Amoco in 1990-94. Carrizo also reviewed 2D and 3D long-offset speculative
seismic acquired by TGS and Veritas, respectively. The reprocessed data was adequate
to map the prospects and it did not appear the long-offset data added significant value in
the evaluation. A seismic stratigraphic study was also completed of the Upper Jurassic
reservoir, including a fault seal/overpressure study to assess overall seal risk.
The Licensee elected not to drill a 3,900m (12,800 ft) well into the Middle Jurassic to
keep the license in good standing and released the block at the end of two years. The
block contains no well control. The nearest well is the 22/8-3 dry hole drilled by Ranger
in 1984 to a depth of 4,600m (15,110 ft) which had gas shows in the U. Cretaceous
section but was dry and abandoned after encountering severe over-pressure in the Fulmar
section (5,000-7,000 psi).
III. Prospectivity Analysis
A.
Reservoir
The Upper Jurassic (Fulmar) sandstone is the only prospective reservoir in the block.
The Paleocene (Forties) horizon showed no obvious AVO response on the 3D seismic
and lacked sufficient closure to be deemed prospective.
B.
Source
The block is broadly underlain by the Fisher Bank Basin with a thick mature Kimmeridge
Clay source rock currently in the oil window on the block.
C.
Seal
The Upper Jurassic Kimmeridge Clay directly overlays the reservoir unit and acts as a
vertical seal. Top seals in this part of the Fisher Bank basin have been blown due to
severe overpressure and must be considered a key risk for the two prospects. Lateral seal
is provided by four-way structural dip closure for Santa Cruz. Santa Cruz North relies on
dip closure to the south and cross-fault seal to the north.
D.
Trap
Santa Cruz is a faulted four-way dip closure (in time and depth) with Upper Jurassic
Fulmar reservoir. Santa Cruz straddles the boundary between blocks 22/8c and 22/13b to
the south with 30% of the prospect extending into block 22/8c. There is low relief
structural closure at the BCU.
Santa Cruz North is a high relief Upper Jurassic closure with Upper Jurassic Fulmar
reservoir. There is no closure at the BCU.
E.
Chance of Success
Overall geologic POS is considered to be 17%, with each of the risk components as
follows: Charge (90%); Structure (85%); Reservoir (75%); Seal (30%). The key risks
are thought to be top seal, reservoir thickness and commercial volumes given success.
F.
Remaining Prospectivity
The license area was comprehensively mapped and no additional prospectivity was
identified.
IV. Maps & Figures
A. Location Map
UK North Sea Index Map
Central North Sea
Block 22/8c
Norway
Santa Cruz Leads/Prospects
Scotland
Block 22/8c
Denmark
Germany
England
Netherlands
B. Prospect Map
Block 22/8c, Prospects
22/8-3
Closure
Santa Cruz North
No BCU Closure
Small Closure
Santa Cruz
22/8c
22/13b
Base Cretaceous
Unconformity
Depth Structure Map
Low relief BCU closure above
Santa Cruz Prospect
Small low relief BCU closure
west of Santa Cruz Prospect
No BCU closure above Santa
Cruz North Prospect
C. I. = 50 ft.
2000 Metres
C. Seismic Profile
Block 22/8c, Prospect
E
W
Santa Cruz
Ekofisk
Santa Cruz
Prospect
X-line 5110
Critical dip closure to
the West-Northwest
Hidra
Upper Jurassic
BCU
Base U. Jurassic
Upper Jurassic seismic
character variable over
the structure
Upper Jurassic interval
thins rapidly towards
the west
1000 Metres
V.
Clearance
Carrizo Oil & Gas, Inc. confirms that DBERR is free and clear to publish this
relinquishment report.